Walter Willett, of Harvard's School of Public Health, says most overweight people will benefit from some weight loss. / Handout

by Nanci Hellmich, USA TODAY

by Nanci Hellmich, USA TODAY

A controversial new government study released this week has shaken some dieters' resolutions to lose weight.

The research showed that people who are moderately heavy, up to 30 or so pounds above normal, have a slightly lower risk (6%) of premature death than those at a normal weight.

But those who are extremely obese -- roughly 60 or more pounds over a normal weight -- have a 29% greater risk of dying early than those who are at a normal weight, according to the review of 97 studies, conducted by researchers at the National Center for Health Statistics, part of the Centers for Disease Control and Prevention. The scientists looked at deaths from all reasons and people's body mass index (BMI), a number that considers weight and height.

The research, which got widespread news coverage, is causing some to think that their extra weight may not be the health danger that they thought it was. Are these reactions justified?

USA TODAY turned to two experts for answers: Thomas Frieden, director of the Centers for Disease Control and Prevention, and Walter Willett, chair of the nutrition department at the Harvard School of Public Health.

Q: Do you think being a few pounds to 30 pounds over a normal weight is hazardous to your health?

Frieden: Yes, I think that increased weight carries a number of health risks, but not all weight is the same. If you work out and build muscle mass, you may increase weight and that's healthy. The study that came out this week was about death rates, it didn't cover type 2 diabetes and other health risks, which we know increase with weight.

Willett: The hazards of being a few pounds overweight partly depend on how someone got there. If someone has always been muscular and is active and strong, and their blood pressure and levels of (blood) glucose and cholesterol are fine, then their health risks are probably minimal. However, if someone has gotten to this weight by putting on 10 pounds or more, has increased their waistline by more than 2 inches, or has elevations in blood pressure, glucose or cholesterol, then this weight can be a serious health risk.

Q: Should people try to lose weight if they are overweight?

Frieden: The key is to do things that you can stick with. Find physical activities you love doing, and do more of them -- whether that's walking or sports or playing with your kids or dancing. Being physically active is very important at any weight. Similarly, find healthy foods that you love and eat more of them, and less of unhealthy things.

Willett: The large majority of overweight people have gotten there because they have added weight as adults, and almost all will have some metabolic abnormalities (such as high blood pressure) because of this. Thus, most people who are overweight will benefit from some weight loss, even if it is only a 5% loss. Even more important, for those who are not yet overweight, a weight gain of 5 pounds after age 20, even in the normal range, is a signal to pay more attention to daily physical activity and diet to prevent becoming overweight.

Q: Why do you think the research found that those who are overweight are at a slightly lower risk of early death?

Frieden: The science on this is complicated. There are two big unknowns. The first is what is the right method to study the relationship between body mass index and death rates. There is scientific discussion about what's the best way to do that. The second is whether BMI is the best measure. We know that BMI is an imperfect measure. Someone who is very muscular may show up as overweight when in fact they are at a healthy weight. We also know that for certain populations the health risks appear at a lower BMI. Things like waist circumference and skin-fold thickness may be more accurate for some types of analysis. But BMI is easy to use in large epidemiological studies.

Willett: The most serious problem in the paper is that the normal-weight group included a mix of lean and active people, heavy smokers, patients with cancer (and) other conditions that cause weight loss, and frail elderly people who had lost weight due to rapidly declining health. Because the overweight and obese groups were compared to this mix of healthy and ill persons who have a very high risk of death, this led to the false conclusions that being overweight is beneficial and that grade 1 (moderate) obesity carries no extra risk.

The new statistics are completely misleading for anyone interested in knowing about their optimal weight. ... The paper is a pile of rubbish.

In the last several years, two other major analyses, involving the collaborative efforts of more than 150 scientists, have been conducted on the relation of body weight to mortality. These were far superior to the recent paper because they combined the original data from over 70 studies. After eliminating distortions due to the effects of serious disease on body weight, these studies showed clearly that both overweight and all grades of obesity are associated with increased mortality.

Q: What is your advice to people who are 60 or more pounds overweight?

Frieden: Take one step at a time. You can't run before you walk. Start by walking. Have reasonable goals of being more physically active and eating a healthier diet. It's not easy to make changes -- that's why it's so important that you make changes you can stick with. Most people can't stick with a regimen they hate.

Willett: This amount of overweight is a major threat to health and greatly increases risks of type 2 diabetes, heart disease, cancer, arthritis and many other conditions. It will be important to work with your health care provider to find the best approach, but in most cases this will be a combination of increased physical activity and healthier eating. Often, group support will be helpful, and in a few situations the addition of medication or surgery will be appropriate.